1). Field of the Invention
This invention relates to a method of constructing an electronic assembly and to an electronic assembly which may be made according to the method of the invention.
2). Discussion of Related Art
Integrated circuits are formed on semiconductor wafers. The wafers are then sawed into semiconductor chips. Each semiconductor chip is then mounted to a package substrate. An integrated circuit within the semiconductor chip can be powered up and data signals can be sent to and received from the integrated circuit via the package substrate.
When the integrated circuit is powered up, heat is generated on the semiconductor chip which could cause destruction of the integrated circuit if the heat is not transferred away. A thermally conductive plate is often located next to the semiconductor chip. A thermally conductive grease may be located between the semiconductor chip and the thermally conductive plate. The thermally conductive grease contacts the semiconductor chip and the thermally conductive plate on opposing sides and acts as a thermal couple between the semiconductor chip and the thermally conductive plate. Heat can then be transferred from the semiconductor chip through the grease to the thermally conductive plate, from where heat can be transferred to a heat sink or other device and be convected into the ambient.
The use of a grease as a thermal couple is often unsuitable for high power applications. A thermally conductive grease does not transfer a sufficient amount of heat when a large amount of heat is generated on a semiconductor chip. One reason why a thermally conductive grease is not a good conductor of heat is because there are no metals in a thermally conductive grease. Metals, on the other hand, are usually also electrically conductive. The use of a metal as a thermal couple is therefore usually avoided because an electrically conductive metal may cause shorting between components of the semiconductor chip or the package substrate.
According to one aspect of the invention a method of constructing an electronic assembly is provided. The electronic assembly is constructed from a semiconductor package including a package substrate and a semiconductor chip mounted to the package substrate, a thermally conductive member, and a substance including indium. The method comprises securing the thermally conductive member and the semiconductor package in a selected orientation relative to one another with the thermally conductive member on a side of the semiconductor chip opposing the package substrate and with the substance located between the semiconductor chip and at least a portion of the thermally conductive member. The substance is thermally coupled to the semiconductor chip on one side and thermally coupled to the portion of the thermally conductive member on an opposing side.